This invention relates to novel spiroazabicyclic heterocyclic amines or pharmaceutically acceptable salts thereof, processes for preparing them, pharmaceutical compositions containing them and their use in therapy. A further object is to provide active compounds which are potent ligands for nicotinic acetylcholine receptors (nAChR""s).
The use of compounds which bind nicotinic acetylcholine receptors in the treatment of a range of disorders involving reduced cholinergic function such as Alzheimer""s disease, cognitive or attention disorders, anxiety, depression, smoking cessation, neuroprotection, schizophrenia, analgesia, Tourette""s syndrome, and Parkinson""s disease has been discussed in McDonald et al. (1995) xe2x80x9cNicotinic Acetylcholine Receptors: Molecular Biology, Chemistry and Pharmacologyxe2x80x9d, Chapter 5 in Annual Reports in Medicinal Chemistry, vol. 30, pp. 41-50, Academic Press Inc., San Diego, Calif.; and in Williams et al. (1994) xe2x80x9cNeuronal Nicotinic Acetylcholine Receptors,xe2x80x9d Drug News and Perspectives, vol. 7, pp. 205-223.
U.S. Pat. No. 5,468,875 discloses N-alkylcarbamic acid 1-azabicyclo[2.2.1]hept-3-yl esters which are centrally active muscarinic agents useful in the treatment of Alzheimer""s disease and other disorders.
N-(2-alkoxyphenyl)carbamic acid 1-azabicyclo[2.2.2]octan-3-yl esters are disclosed in Pharmazie, vol. 48, 465-466 (1993) along with their local anesthetic activity. N-phenylcarbamic acid 1-azabicyclo[2.2.2]octan-3-yl esters substituted at the ortho position on the phenyl ring are described as local anaesthetics in Acta Pharm. Suecica, 7, 239-246 (1970).
Furopyridines useful in controlling synaptic transmission are disclosed in WO 97/05139.
According to the invention it has been found that a compound of formula I 
wherein n is 0 or 1;
m is 0 or 1;
p is 0 or 1;
Y is CH, N or NO
X is oxygen or sulfur;
W is oxygen, H2 or F2;
A is N or C(R2);
G is N or C(R3);
D is N or C(R4);
with the proviso that no more than one of A, G, and D is nitrogen but at least one of Y, A, G, and D is nitrogen or NO;
R1 is hydrogen or C1-C4 alkyl;
R2, R3, and R4 are independently hydrogen, halogen, C1-C4 alkyl, C2-C4 alkenyl, C2-C4 alkynyl, aryl, heteroaryl, OH, OC1-C4 alkyl, CO2R1, xe2x80x94CN, xe2x80x94NO2, xe2x80x94NR5R6, xe2x80x94CF3, xe2x80x94OSO2CF3, or R2 and R3, or R3 and R4, respectively, may together form another six membered aromatic or heteroaromatic ring sharing A and G, or G and D, respectively containing between zero and two nitrogen atoms, and substituted with one to two of the following substituents: independently hydrogen, halogen, C1-C4 alkyl, C2-C4 alkenyl, C2-C4 alkynyl, aryl, heteroaryl, OH, OC1-C4 alkyl, CO2R1, xe2x80x94CN, xe2x80x94NO2, xe2x80x94NR5R6, xe2x80x94CF3, OSO2CF3;
R5 and R6 are independently hydrogen, C1-C4 alkyl, C(O)R7, C(O)NHR8, C(O)OR9, SO2R10 or may together be (CH2)jQ(CH2)k where Q is O, S, NR11, or a bond;
j is 2 to 7;
k is 0 to 2;
R7, R8, R9, R10, and R11 are independently C1-C4 alkyl, aryl, or heteroaryl, or an enantiomer thereof, and the pharmaceutically acceptable salts thereof is a potent ligand for nicotinic acetylcholine receptors.
Unless otherwise indicated, the C1-C4 alkyl groups referred to herein, e.g., methyl, ethyl, n-propyl, n-butyl, i-propyl, i-butyl, t-butyl, s-butyl, may be straight-chained or branched, and the C3-C4 alkyl groups may also be cyclic, e.g., cyclopropyl, cyclobutyl.
Unless otherwise indicated, the C1-C6 alkyl groups referred to herein, e.g., methyl, ethyl, n-propyl, n-butyl, i-propyl, i-butyl, t-butyl, s-butyl, n-pentyl, i-pentyl, t-pentyl, neo-pentyl, n-hexyl, or i-hexyl may be straight-chained or branched, and the C3-C6 alkyl groups may also be cyclic, e.g., cyclopropyl, cyclobutyl, cyclopentyl or cyclohexyl.
Unless otherwise indicated, the C1-C4 alkoxy groups referred to herein, e.g., methoxy, ethoxy, n-propoxy, i-propoxy, n-butoxy, i-butoxy, t-butoxy, s-butoxy, may be straight-chained or branched.
Unless otherwise indicated, the C2-C4 alkenyl groups referred to herein may contain one or two double bonds, e.g., ethenyl, i-propenyl, n-butenyl, i-butenyl, allyl, 1,3-butadienyl.
Unless otherwise indicated, the C2-C4 alkynyl groups referred to herein contain one triple bond, e.g., ethynyl, propynyl, 1- or 2-butynyl.
Halogen referred to herein may be fluoride, chloride, bromide, or iodide.
Unless otherwise indicated, aryl refers to a phenyl ring optionally substituted with one to three of the following substituents: hydrogen, halogen, C1-C4 alkyl, C2-C4 alkenyl, C2-C4 alkynyl, OH, OC1-C4 alkyl, CO2R1, xe2x80x94CN, xe2x80x94NO2, xe2x80x94NR5R6, xe2x80x94CF3;
Unless otherwise indicated, heteroaryl refers to a five- or six-membered aromatic ring containing one or two nitrogen atoms, such as pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl, pyrrolyl, imidazolyl or pyrazolyl, with the carbon atoms of that ring optionally substituted with one to three of the following substituents: hydrogen, halogen, C1-C4 alkyl, C2-C4 alkenyl, C2-C4 alkynyl, OH, OC1-C4 alkyl, CO2R1, xe2x80x94CN, xe2x80x94NO2, xe2x80x94NR5R6, xe2x80x94CF3; R5 and
R6 may together be (CH2)jQ(CH2)k where Q is O, S, N11, or a bond, and where j is 2 to 7, preferably 2 to 3, and k is 0 to 2, so as to form a 3-7 membered ring, preferably a 5- or 6-membered ring, for example pyrrolidinyl, imidazolidinyl piperazinyl, piperidyl, morpholinyl, or thiomorpholinyl.
R2 and R3 may together form another six membered aromatic or heteroaromatic ring sharing A and G containing between zero and two nitrogen atoms refers to groups such as quinoline, 1,5-, 1,6-, 1,7-, or 1,8-diazanaphthalene.
R3 and R4 may together form another six membered aromatic or heteroaromatic ring sharing G and D containing between zero and two nitrogen atoms refers to groups such as isoquinoline, 2,5-, 2,6-, 2,7-, or 2,8-diazanaphthalene.
Preferred compounds of the invention are compounds of formula I wherein m is 1; n is 0; p is 0; X is oxygen; W is H2; A is C(R2); G is C(R3); D is C(R4).
Preferred compounds of the invention include the following:
spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-bromospiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-phenylspiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-nitrospiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)xe2x80x94 furo[2,3-b]pyridine];
1xe2x80x2-chlorospiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]isoquinoline];
5xe2x80x2-(phenylcarboxanido)spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H))furo[2,3-b]pyridine];
5xe2x80x2-(phenylaminocarbonylamino)spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-(phenylsulfonylamido)spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-aminospiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-N-methylaminospiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-N,N-dimethylaminospiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];5xe2x80x2-N,N-diethylaminospiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-N-ethylaminospiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-N-benzylaminospiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-N-formamidospiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3 xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-N-acetamidospiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3 xe2x80x2H)-furo[2,3-b]isoquinoline];
spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]quinoline];
5xe2x80x2-ethenylspiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-(E)-(phenylethenyl)spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-(4-morpholino)spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-(1-azetidinyl)spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-(E)-(2-(4-pyridyl)ethenyl)spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-(E)-(2-(2-pyridyl)ethenyl)spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-(2-trimethylsilylethynyl)spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-ethynylspiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-(2-furyl)spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-(3-pyridyl)spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-methylspiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine-5xe2x80x2carbonitrile];
spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine-5xe2x80x2carboxamide];
5xe2x80x2-Nxe2x80x2-(3-chlorophenyl)aminocarbonylminospiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-Nxe2x80x2-(2-nitrophenyl)aminocarbonylaminospiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
4xe2x80x2-chlorospiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
4xe2x80x2-methoxyspiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
4xe2x80x2-phenylthiospiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
4xe2x80x2-(N-2-aminoethyl)aminospiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
4xe2x80x2-phenylaminospiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
4xe2x80x2-methylaminospiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
4xe2x80x2-(4-N-methylpiperazin-1-yl)spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
4xe2x80x2-chloro-spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[3,2-c]pyridine];
spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[3,2-c]pyridine];
spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2(3 xe2x80x2H)-furo[2,3-b]pyridine-7xe2x80x2-oxide];
spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2(3xe2x80x2H)-furo[2,3-b]pyridine-6xe2x80x2-carbonitrile];
6xe2x80x2-chlorospiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2(3xe2x80x2H)-furo[2,3-b]pyridine];
6xe2x80x2-fluorospiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2(3xe2x80x2H)-furo[2,3-b]pyridine]; and the enantiomers, and pharmaceutically acceptable salts thereof.
Particularly preferred compounds of the invention are compounds of formula I wherein m is 1; n is 0; p is 0; X=oxygen; W is H2; A=CH, D=CH, and G=C(R3), including the following compounds:
spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2(3xe2x80x2H)-furo[2,3-b]pyridine-7xe2x80x2-oxide];
5xe2x80x2-bromospiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-phenylspiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-nitrospiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-(phenylcarboxamido)spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-(phenylaminocarbonylamino)spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-(phenylsulfonylamido)spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-aminospiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-N-methylaminospiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-N,N-dimethylaminospiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine]; 5xe2x80x2-N,N-diethylaminospiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-N-ethylaminospiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-N-benzylaminospiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-N-formamidospiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-N-acetamidospiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-ethenylspiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-(E)-(phenylethenyl)spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-(4-morpholino)spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-(1-azetidinyl)spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-(E)-(2-(4-pyridyl)ethenyl)spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-(E)-(2-(2-pyridyl)ethenyl)spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-(2-trimethylsilylethynyl)spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-ethynylspiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-(2-furyl)spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-(3-pyridyl)spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-methylspiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine-5xe2x80x2carbonitrile];
spiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine-5xe2x80x2carboxamide];
5xe2x80x2-Nxe2x80x2-(3-chlorophenyl)aminocarbonylminospiro[1-azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
5xe2x80x2-Nxe2x80x2-(2-nitrophenyl)aminocarbonylaminospiro[1azabicyclo[2.2.2]octane-3,2xe2x80x2-(3xe2x80x2H)-furo[2,3-b]pyridine];
Methods of Preparation
In the reaction schemes and text that follow, A, G, D, X, W, Y, Z, m, n, and p, unless otherwise indicated, are as defined above for formula I.
(A) Compounds wherein p is 0 and Y is N
The compounds of formula I, wherein p is 0 and Y is N, may be prepared according to the methods outlined in Scheme I. 
Compounds of formula I where Wxe2x95x90H2 and p is 0 may be prepared from the deprotection of a compound of formula IIA using acid in a suitable solvent. Suitable acids include mineral, organic and Lewis acids, for example, hydrochloric and hydrobromic acid, sulfuric acid, triflic acid, methanesulfonic acid, and boron trifluoride etherate. The preferred acid is hydrobromic acid. Suitable solvents include acetone, butanone, ethanone, and pinacolone. The preferred solvent is acetone. The reaction is usually conducted at a temperature from about xe2x88x9210xc2x0 C. to about 100xc2x0 C., preferably about 0xc2x0 C. to about 60xc2x0 C. Alternatively the deprotection may be conducted by heating the borane complex in alcoholic solvents. A preferred method is by refluxing a ethanolic solution of the complex.
Compounds of formula I where Wxe2x95x90O (oxygen) and p is 0 may be prepared by the oxidation of compounds of formula IIA, for example using selenium dioxide, or by reaction first with N-bromosuccinimide then with sodium bicarbonate and methylsulfoxide, followed by removal of the borane group as described above.
Compounds of formula I where Wxe2x95x90F2 and p is 0 may be prepared from compounds of formula I where Wxe2x95x90O by reaction with a fluorinating agent, for example diethylaminosulfur trifluoride.
Compounds of formula IIA may be prepared from the cyclization of a compound of formula III wherein L is fluoro, chloro, bromo, iodo, xe2x80x94OCH3, xe2x80x94SPh, xe2x80x94SCH3, xe2x80x94SO2Ph, or xe2x80x94SO2CH3 in the presence of a base in an inert solvent. Suitable bases include sodium hydride, sodium amide, potassium hydride, potassium t-amylate, potassium t-butoxide, and potassium bis(trimethylsilyl)amide. The preferred base is sodium hydride. Suitable inert solvents include N,N-dimethylformamide, N-methylpyrrolidin-2-one, ethers such as diethyl ether, tetrahydrofuran, and 1,4-dioxane, and dimethylsulfoxide. The preferred inert solvent is N,N-dimethylformamide. The reaction is usually conducted at a temperature from about 10xc2x0 C. to about 100xc2x0 C., preferably about 20xc2x0 C. to about 66xc2x0 C.
Compounds of formula III wherein L is fluoro, chloro, bromo, iodo, xe2x80x94OCH3, xe2x80x94SPh, xe2x80x94SCH3, xe2x80x94SO2Ph, or xe2x80x94SO2CH3 may be prepared by the reaction of a compound of formula IV with a compound of formula V wherein L is defined as above in an inert solvent. Suitable inert solvents include diethyl ether, tetrahydrofuran and 1,4-dioxane. The preferred inert solvent is tetrahydrofuran. The reaction is usually conducted at a temperature from about xe2x88x92100xc2x0 C. to about 0xc2x0 C., preferably about xe2x88x9278xc2x0 C. to about xe2x88x9225xc2x0 C.
Compounds of formula V wherein L is defined as above may be prepared from a compound of formula VIII wherein L is defined as above using a lithium base and a proton transfer agent in an inert solvent. Suitable lithium bases include lithium diisopropylamide, n-butyllithium, sec-butyllithium, tert-butyllithium, and phenyllithium. The preferred lithium base is phenyllithium. Suitable proton transfer agents include hindered secondary amines such as diisopropylamine and 2,2,6,6-tetramethylpiperidine. The preferred proton transfer agent is diisopropylamine. Suitable inert solvents include diethyl ether, tetrahydrofuran and 1,4-dioxane. The preferred inert solvent is tetrahydrofuran. The reaction is usually conducted at a temperature from about xe2x88x92100xc2x0 C. to about 0xc2x0 C., preferably about xe2x88x9278xc2x0 C. to about xe2x88x9225xc2x0 C. Compounds of formula V are usually taken directly into the reaction with compounds of formula IV without purification.
Compounds of formula IV may be prepared from the reaction of a compound of formula VI with borane (BH3 or B2H6) in an inert solvent. Borane in tetrahydrofuran is preferred. Suitable inert solvents include diethyl ether, tetrahydrofuran and 1,4-dioxane. The preferred inert solvent is tetrahydrofuran. The reaction is usually conducted at a temperature from about xe2x88x9210xc2x0 C. to about 66xc2x0 C., preferably about 0xc2x0 C. to about 20xc2x0 C.
Compounds of formula VIII are known, e.g., either commercially available or may be prepared by methods known to one skilled in the art (see e.g, The Chemistry of Heterocyclic Compounds, Pyridine and Its Derivatives, Part 1, E. Klingsberg, Ed., Interscience Publishers, Inc, NY, 1960).
Compounds of formula VI may be prepared from compounds of formula VII by methods known to one skilled in the art. For example, compounds of formula VI wherein X represents oxygen may be prepared from the corresponding compound of formula VII wherein X represents the oxygen of a ketone using one of the reagents well known in the art for preparation of oxiranes from ketones (see e.g. the reactions referenced in J. March, xe2x80x9cAdvanced Organic Chemistryxe2x80x9d (1985) 3rd Edition, page 1161). Compounds of formula VI wherein X represents sulfur may be prepared from the corresponding compound of formula VII wherein X represents either oxygen or sulfur using one of the methods well known in the art for preparation of episulfides from ketones or thioketones (see, e.g. the reactions referenced in J. March, xe2x80x9cAdvanced Organic Chemistryxe2x80x9d (1985) 3rd Edition, pages 866-867).
Compounds of formula VII are known, e.g., either commercially available or may be prepared by methods known to one skilled in the art (see, e.g, The Chemistry of Heterocyclic Compounds, Heterocyclic Systems with Bridgehead Nitrogen Atoms, Part 2, W. L. Mosby, Ed., Interscience Publishers, Inc, NY, 1961).
(B) Compounds wherein p is 1 and Y is N
The compounds of formula I (p=1) may be prepared according to the methods described in Scheme II or Scheme III, below. 
Compounds of formula I where W is H2 and p is 1 may be prepared from the deprotection of a compound of formula IX using acid in a suitable solvent. Suitable acids include mineral, organic and Lewis acids, for example, hydrochloric and hydrobromic acid, sulfuric acid, triflic acid, methanesulfonic acid and borontrifluoride etherate. The preferred acid is hydrobromic acid. Suitable solvents include acetone, butanone, ethanone, and pinacolone. The preferred solvent is acetone. The reaction is usually conducted at a temperature from about xe2x88x9210xc2x0 C. to about 100xc2x0 C., preferably about 0xc2x0 C. to about 60xc2x0 C. Alternatively the deprotection may be conducted by heating the borane complex in alcoholic solvents. A preferred method is by refluxing a ethanolic solution of the complex.
Compounds of formula I where Wxe2x95x90O and p is 1 may be prepared by the oxidation of compounds of formula I, where W is H2 and p is 1, using selenium dioxide, or by reaction first with N-bromosuccinimide then with sodium bicarbonate and methylsulfoxide, followed by removal of the borane group as described above.
Compounds of formula I, where Wxe2x95x90F2 and p is 1, may be prepared from compounds of formula I, where Wxe2x95x90O and p is 1, by reaction with diethylaminosulfur trifluoride.
Compounds of formula IX may be prepared from the cyclization of a compound of formula X wherein L is fluoro, chloro, bromo, iodo, xe2x80x94OCH3, xe2x80x94SPh, xe2x80x94SCH3, xe2x80x94SO2Ph, or xe2x80x94SO2CH3 in the presence of a base in an inert solvent. Suitable bases include sodium hydride, sodium amide, potassium hydride, potassium t-amylate, potassium t-butoxide, and potassium bis(trimethylsilyl)amide. The preferred base is sodium hydride. Suitable inert solvents include N,N-dimethylformamide, N-methylpyrrolidin-2-one, ethers such as diethyl ether, tetrahydrofuran, and 1,4-dioxane, and dimethylsulfoxide. The preferred inert solvent is N,N-dimethylformamide. The reaction is usually conducted at a temperature from about xe2x88x9210xc2x0 C. to about 100xc2x0 C., preferably about 20xc2x0 C. to about 66xc2x0 C.
Compounds of formula X wherein L is fluoro, chloro, bromo, iodo, xe2x80x94OCH3, xe2x80x94SPh, xe2x80x94SCH3, xe2x80x94SO2CH3 may be prepared by the reaction of a compound of formula XI with a compound of formula V wherein L is defined as above in an inert solvent. Suitable inert solvents include diethyl ether, tetrahydrofuran and 1,4-dioxane. The preferred inert solvent is tetrahydrofuran. The reaction is usually conducted at a temperature from about xe2x88x92100xc2x0 C. to about 0xc2x0 C., preferably about xe2x88x9278xc2x0 C. to about xe2x88x9225xc2x0 C.
Compounds XI, wherein P is xe2x80x94SO2Ph, xe2x80x94SO2PhCH3xe2x80x944, xe2x80x94SO2CH3 or xe2x80x94SO2CF3 may be prepared from compounds XII by reaction with a reagent such as toluenesulfonyl chloride, methanesulfonyl chloride, or trifluoromethanesulfonyl chloride in the presence of an amine base such as triethylamine, dimethylaminopyridine, or diazabicyclo[4.3.0]nonane in an inert solvent. Suitable inert solvents may be dichloromethane, chloroform, tetrahydrofuran, diethyl ether, or dioxane. The preferred inert solvent is dichloromethane. The reaction is usually conducted at a temperature from about xe2x88x9210xc2x0 C. to about 66xc2x0 C., preferably about 0xc2x0 C. to about 20xc2x0 C.
Compounds XII may be prepared from compounds of formula XIII by reduction with reagents such as lithium aluminum hydride, sodium bis(2-methoxyethoxy)aluminum hydride, sodium or lithium triethylboride, lithium tri-sec-butylborohydride, potassium tri-sec-butylborohydride, sodium tri-sec-butylborohydride or lithium borohydride. The preferred reagent is lithium borohydride. Suitable inert solvents include diethyl ether, tetrahydrofuran and 1,4-dioxane. The preferred inert solvent is tetrahydrofuran. The reaction is usually conducted at a temperature from about xe2x88x9278xc2x0 C. to about 66xc2x0 C., preferably about xe2x88x9210xc2x0 C. to about 20xc2x0 C.
Compounds of formula XIII, wherein R is C1-C6 alkyl, xe2x80x94CH2xe2x80x94Ar, or Ar, where Ar is phenyl optionally substituted with one to three of the following substitutents: halogen, C1-C4 alkyl, or C1-C4 alkoxy, may be prepared from the reaction of a compound of formula XIV with borane (BH3 or B2H6) in an inert solvent. Borane in tetrahydrofuran is preferred. Suitable inert solvents include diethyl ether, tetrahydrofuran and 1,4-dioxane. The preferred inert solvent is tetrahydrofuran. The reaction is usually conducted at a temperature from about xe2x88x9210xc2x0 C. to about 66xc2x0 C., preferably about 0xc2x0 C. to about 20xc2x0 C.
Compounds of formula XIV are known, e.g., either commercially available or may be prepared from compounds of formula VII by methods known to one skilled in the art for the preparation of xcex2-hydroxy esters from the reaction of esters and ketones (see, e.g. the reactions referenced in J. March, xe2x80x9cAdvanced Organic Chemistryxe2x80x9d (1985) 3rd Edition, page 439).
Compounds of formula I where W is H2 and p is 1 may be prepared from the cyclization of a compound of formula XVIII wherein L is fluoro, chloro, bromo, iodo, xe2x80x94OCH3, xe2x80x94SPh, xe2x80x94SCH3, xe2x80x94SO2Ph, or xe2x80x94SO2CH3 in the presence of a base in an inert solvent. Suitable bases include sodium hydride, sodium amide, potassium hydride, potassium t-amylate, potassium t-butoxide, and potassium bis(trimethylsilyl)amide. The preferred base is sodium hydride. Suitable inert solvents include N,N-dimethylformamide, N-methylpyrrolidin-2-one, ethers such as diethyl ether, tetrahydrofuran, and 1,4-dioxane, and dimethylsulfoxide. The preferred inert solvent is N,N-dimethylformamide. The reaction is usually conducted at a temperature from about xe2x88x9210xc2x0 C. to about 100xc2x0 C., preferably about 20xc2x0 C. to about 66xc2x0 C.
Compounds of formula XVIII wherein L is defined as above may be prepared by catalytic hydrogenation of a compound of formula XVII using catalysts such as palladium on carbon, palladium hydroxide on carbon, palladium oxide, platinum on carbon, platinum oxide, Raney nickel, or rhenium on carbon in an inert solvent. Suitable inert solvents include methanol, ethanol, aqueous methanol or ethanol and ethyl acetate. The preferred solvent is ethanol. The reaction is usually conducted at a temperature from about 0xc2x0 C. to about 100xc2x0 C., preferably about 20xc2x0 C. to about 50xc2x0 C.
Compounds of formula XVII wherein L is defined as above may be prepared by reaction of a compound of formula XV with a compound of formula XVI using a palladium catalyst, together with a suitable ligand, base, and solvent. Suitable palladium catalysts include palladium acetate. Suitable ligands include phosphine ligands, such as triphenylphosphine or tri-o-tolylphosphine. Suitable bases include amines and inorganic bases, such as triethylamine, diisopropylethylamine, sodium carbonate or tetrabutylammonium acetate. Suitable solvents include dimethylformamide or acetonitrile.The reaction is usually conducted at a temperature from about 0xc2x0 C. to about 140xc2x0 C., preferably about 20xc2x0 C. to about 85xc2x0 C.
Compounds of formula XVI, where L is defined as above and R2 is chloro, bromo, iodo, fluoro, trifluoromethylsulfonyl, toluenesulfonyl or methylsulfonyl may be prepared by literature methods from commercially available materials.
Compounds of formula XV may be prepared from compounds of formula VII by methods known to one skilled in the art for the preparation of allyl alcohols from ketones using vinylmetal salts such as vinylmagnesium bromide.
(C) Compounds wherein p is 0 or 1
Compounds of formula I wherein R2, R3, or R4 is halogen may be prepared from compounds of formula I wherein the corresponding substituent is hydrogen by reaction with a suitable halogenating agent, for example bromine in acetic acid. The transformation may require the addition of an acidic catalyst, such as the corresponding iron trihalide.
Compounds of formula I wherein R2, R3, or R4 is C1-C4 alkyl, C2-C4 alkenyl, C2-C4 alkynyl, aryl, heteroaryl may be prepared from compounds of formula I wherein the corresponding substituent is halogen or OSO2CF3 by reaction with an appropriate alkyl, alkenyl, alkynyl, aryl or heteroaryl stannane reagent, in the presence of a suitable organometallic catalyst, for example tetrakis(triphenylphosphine)palladium (0), in a suitable solvent, for example 1,2-dimethoxyethane.
Compounds of formula I wherein R2, R3, or R4 is aryl, heteroaryl may be prepared from compounds of formula I wherein the corresponding substituent is halogen or OSO2CF3 by reaction with an aryl or heteroaryl boronic acid, in the presence of a suitable organometallic catalyst, for example tetrakis(triphenylphosphine)palladium (0), in a suitable solvent, for example 1,2-dimethoxyethane.
Compounds of formula I wherein R2, R3, or R4 is NO2 may be prepared from compounds of formula I wherein the corresponding substituent is hydrogen by nitration using a suitable nitrating agent, for example nitric acid in concentrated sulfuric acid.
Compounds of formula I wherein R2, R3, or R4 is NH2 may be prepared from compounds of formula I wherein the corresponding substituent is NO2 by reduction using a suitable procedure, for example hydrogenation. Hydrogenation may be performed by the reaction of a compound, dissolved in a suitable solvent, with gaseous hydrogen in the presence of a suitable catalyst. Suitable solvents include methanol, ethanol, and acetic acid. Suitable catalysts include palladium, for example as 10% palladium on carbon.
Compounds of formula I wherein R2, R3, or R4 is NR5R6 wherein R6 is alkyl may be prepared from compounds of formula I wherein the corresponding substituent is NHR5 by a suitable alkylation procedure. Also, compounds of formula I wherein R2, R3, or R4 is NR5R6 wherein R5 and R6 are identical alkyl groups or R5 and R6 together are (CH2)jQ(CH2)k may be prepared from compounds of formula I wherein the corresponding substituent is NH2 by a suitable alkylation procedure. Suitable alkylation procedures may include treatment with a suitable alkyl halide or sulfonate ester and base, for example sodium hydride, in a suitable solvent, for example DMF, or treatment with a suitable aldehyde or ketone in the presence of an acidic catalyst, for example zinc chloride, a reducing agent, for example sodium cyanoborohydride, and solvent, for example ethanol.
Compounds of formula I wherein R2, R3, or R4 is OSO2CF3 may be prepared from compounds of formula I wherein the corresponding substituent is OH by reaction with trifluoromethanesulfonic anhydride in the presence of a suitable base, for example 2,6-di-t-butylpyridine, in a suitable solvent, for example dichloromethane.
Compounds of formula I wherein R2, R3, or R4 is NR5R6 may also be prepared from compounds of formula I wherein the corresponding substituent is halide or OSO2CF3 by substitution with the appropriate amine NHR5R6. Suitable procedures include nucleophilic displacement, involving treatment with the amine, in excess or in the presence of an added base, and a suitable solvent, for example DMSO, or organometallic complex catalysed substitution, involving treatment with the amine in the presence of a suitable organometallic complex, for example complexes of palladium with chelating phosphine ligands, as described in J. Org. Chem., 1996, vol. 61, pp. 7240.
Compounds of formula I wherein R2, R3, or R4 is NR5C(O)R7 may be prepared from compounds of formula I wherein the corresponding substituent is NH2 by a suitable acylation procedure. Suitable acylation procedures include treatment with a carboxylic acid chloride R6C(O)Cl in the presence of an optional nucleophilic catalyst, such as 4-(N,N-dimethylamino)pyridine, a base, for example pyridine or triethylamine, and a suitable solvent, for example tetrahydrofuran, or, alternatively, treatment with a carboxylic acid R6C(O)OH with a coupling agent, for example 1,3-dicyclohexylcarbodiimide, in a suitable solvent, for example tetrahydrofuran.
Compounds of formula I wherein R2, R3, or R4 is NR5C(O)NHR8 may be prepared from compounds of formula I wherein the corresponding substituent is NHR5 by treatment with the appropriate isocyanate R8NCO in a suitable solvent, for example tetrahydrofuran.
Compounds of formula I wherein R2, R3, or R4 is NR5C(O)OR9 may be prepared from compounds of formula I wherein the corresponding substituent is NHR5 by treatment with an appropriate oxychloride or carbonate in the presence of an optional nucleophilic catalyst, such as 4-(N,N-dimethylamino)pyridine, a base, for example pyridine or triethylamine, and a suitable solvent, for example tetrahydrofuran.
Compounds of formula I wherein R2, R3, or R4 is NR5SO2R10 may be prepared from compounds of formula I wherein the corresponding substituent is NHR5 by treatment with an appropriate sulfonyl chloride in a suitable solvent, such as pyridine.
Compounds of formula I wherein R2, R3, or R4 is CN may be prepared from compounds of formula I wherein the corresponding substituent is halide or OSO2CF3 by reaction with a cyanide salt, in a suitable solvent, with the addition of a suitable catalyst possibly also being required. Suitable cyanide salts include copper (I) cyanide, sodium cyanide, sodium dicyanocuprate, or potassium cyanide, and suitable solvents include N,N-dimethylformamide, dimethylsulfoxide, or pyridine. Catalysts which may facilitate the transformation include copper (I) oxide, tetrakis(triphenylphosphine)palladium (0), or nickel (0) complexes generated in situ from dibromobis(triphenylphosphine)nickel(ii), zinc and triphenylphosphine.
Compounds of formula I wherein R2, R3 or R4 is OH, OC1-C4 alkyl may be prepared either from an appropriately substituted 2-chloropyridine or via chemical transformation from another substituent e.g; the OH derivative from the NH2 via the diazo intermediate.
Where necessary, hydroxy, amino, or other reactive groups may be protected using a protecting group as described in the standard text xe2x80x9cProtecting Groups in Organic Synthesisxe2x80x9d, 2nd Edition (1991) by Greene and Wuts.
Compounds of Formula I may be prepared from other compounds of Formula I by using general methods known to one skilled in the art for interconversion of functional groups (see, e.g. the reactions referenced in J. March, xe2x80x9cAdvanced Organic Chemistryxe2x80x9d (1985) 3rd Edition).
Also, several of the substituted compounds of Formula I may be prepared by using an appropriately substituted compound of Formula Vim, viz., 2-chloro-5-trifluoromethylpyridine would yield the R3 is CF3.
The above described reactions, unless otherwise noted, are usually conducted at a pressure of about one to about three atmospheres, preferably at ambient pressure (about one atmosphere). Unless otherwise stated, the above described reactions are conducted under an inert atmosphere, preferably under a nitrogen atmosphere.
The compounds of the invention and intermediates may be isolated from their reaction mixtures by standard techniques.
Acid addition salts of the compounds of formula I which may be mentioned include salts of mineral acids, for example the hydrochloride and hydrobromide salts; and salts formed with organic acids such as formate, acetate, maleate, benzoate, tartrate, and fumarate salts.
Acid addition salts of compounds of formula I may be formed by reacting the free base or a salt, enantiomer or protected derivative thereof, with one or more equivalents of the appropriate acid. The reaction may be carried out in a solvent or medium in which the salt is insoluble or in a solvent in which the salt is soluble, e.g., water, dioxane, ethanol, tetrahydrofuran or diethyl ether, or a mixture of solvents, which may be removed in vacuum or by freeze drying. The reaction may be a metathetical process or it may be carried out on an ion exchange resin.
The compounds of formula I exist in tautomeric or enantiomeric forms, all of which are included within the scope of the invention. The various optical isomers may be isolated by separation of a racemic mixture of the compounds using conventional techniques, e.g. fractional crystallization, or chiral HPLC. Alternatively the individual enantiomers may be made by reaction of the appropriate optically active starting materials under reaction conditions which will not cause racemization.
(D) Compounds wherein Y is NO
Compounds of formula I, wherein Y is NO, X is oxygen, A is C(R2), G is C(R3) and D is C(R4), may be prepared from compounds of formula XIX, wherein X is oxygen, A is C(R2), G is C(R3) and D is C(R4), by reduction with a suitable reducing agent under suitable conditions, for example sulfur dioxide in ethanol at ambient temperature. 
Compounds of formula XIX may be prepared from compounds of formula I wherein Y is N, X is oxygen, A is C(R2), G is C(R3) and D is C(R4), by oxidation with a suitable oxidising agent under suitable conditions, for example aqueous hydrogen peroxide in acetic acid at reflux temperature.
Compounds of the formula I wherein Y is N, X is oxygen, A is C(R2), G is C(R3) and D is C(R4), may be prepared in analogy with sections (A), (B) and (C), above.
Compounds of formula I, in which Y is N and A is C(R2), wherein R2 is hydroxyl, may be prepared from compounds of formula I in which Y is NO by rearrangement using a carboxylic anhydride in a suitable solvent, for example trifluoroacetic anhydride in DMF;
Compounds of formula I in which Y is N and A is C(R2), wherein R2 is halogen, may be prepared from compounds of formula I in which Y is NO and A is C(R2), wherein R2 is hydrogen, by reaction with a phosphorus halide or oxyhalide, either neat or with a suitable co-solvent, for example neat phosphorus oxychloride.
Compounds of formula I in which Y is N and A is C(R2), wherein R2 is CN, may be prepared from compounds of formula I in which Y is NO and A is C(R2), wherein R2 is hydrogen, by reaction with a suitable cyanide source such as trimethylsilyl cyanide in the presence of a suitable base, for example triethylamine, in a suitable solvent, for example acetonitrile.
Intermediates
A further aspect of the invention relates to new intermediates. Special interest among these new intermediates are the borane containing compounds, especially the compound of formula II in Scheme I and the compound of formula XIII in Scheme II. These intermediates are useful in the synthesis of compounds of formula I, but their use is not limited to the synthesis of said compounds;
Thus, compounds of the formula II 
wherein n is 0 or 1;
m is 0 or 1;
p is 0 or 1;
X is oxygen or sulfur;
W is oxygen, H2 or F2;
A is N or C(R2);
G is N or C(R3);
D is N or C(R4);
with the proviso that no more than one of A, G, and D is nitrogen;
R1 is hydrogen or C1-C4 alkyl;
R2, R3, and R4 are independently hydrogen, halogen, C1-C4 alkyl, C2-C4 alkenyl, C2-C4 alkynyl, aryl, heteroaryl, OH, OC1-C4 alkyl, CO2R1, xe2x80x94CN, xe2x80x94NO2, xe2x80x94NR5R6, xe2x80x94CF3, xe2x80x94OSO2CF3 or R2 and R3, or R3 or R4, respectively, may together form another six membered aromatic or heteroaromatic ring sharing A and G, or G and D, respectively, containing between zero and two nitrogen atoms, and substituted with one to two of the following substituents: independently hydrogen, halogen, C1-C4 alkyl, C2-C4 alkenyl, C2-C4 alkynyl, aryl, heteroaryl, OH, OC1-C4 alkyl, CO2R1, xe2x80x94CN, xe2x80x94NO2, xe2x80x94NR5R6, xe2x80x94CF3, xe2x80x94OSO2CF3;
R5 and R6 are independently hydrogen, C1-C4 alkyl, C(O)R7, C(O)NHR8, C(O)OR9, SO2R10 or may together be (CH2)jQ(CH2)k where Q is O, S, NR11, or a bond;
j is 2to 7;
k is 0 to 2;
R7, R8, R9, R10, and R11 are independently C1-C4 alkyl, aryl, or heteroaryl, or an enantiomer thereof.
Compounds of formula XIII 
wherein n is 0 or 1;
m is 0 or 1;
X is oxygen or sulfur;
R1 is hydrogen or C1 to C4 alkyl;
R is C1-C6 alkyl, xe2x80x94CH2xe2x80x94Ar, or Ar;
Ar is phenyl optionally substituted with one to three of the following substitutents: halogen, C1-C4 alkyl, or C1-C4 alkoxy, or an enantiomer thereof.
Intermediate compounds also exist in enantiomeric forms and may be used as purified enantiomers, racemates or mixtures.
Use of compounds IV, III, II, XII, X and IX as intermediates in a synthesis of a ligand for nicotinic acetylcholine receptors is another aspect of the invention.
A further aspect of the invention relates to the utility of compounds of formula I wherein Y is NO as intermediates. These intermediates are useful in the synthesis of compounds of formula I wherein Y is N, but their use is not limited to the synthesis of said compounds.
Pharmaceutical Compositions
A further aspect of the invention relates to a pharmaceutical composition for treating or preventing a condition or disorder as exemplified below arising from dysfunction of nicotinic acetylcholine receptor neurotransmission in a mammal, preferably a human, comprising an amount of a compound of formula I, an enantiomer thereof or a pharmaceutically acceptable salt thereof, effective in treating or preventing such disorder or condition and an inert pharmaceutically acceptable carrier.
For the above-mentioned uses the dosage administered will, of course, vary with the compound employed, the mode of administration and the treatment desired. However, in general, satisfactory results are obtained when the compounds of the invention are administered at a daily dosage of from about 0.1 mg to about 20 mg per kg of animal body weight, preferably given in divided doses 1 to 4 times a day or in sustained release form. For man, the total daily dose is in the range of from 5 mg to 1,400 mg, more preferably from 10 mg to 100 mg, and unit dosage forms suitable for oral administration comprise from 2 mg to 1,400 mg of the compound admixed with a solid or liquid pharmaceutical carrier or diluent.
The compounds of formula I, or an enantiomer thereof, and pharmaceutically acceptable salts thereof, may be used on their own or in the form of appropriate medicinal preparations for enteral or parenteral administration. According to a further aspect of the invention, there is provided a pharmaceutical composition including preferably less than 80% and more preferably less than 50% by weight of a compound of the invention in admixture with an inert pharmaceutically acceptable diluent or carrier.
Examples of diluents and carriers are:
for tablets and dragees: lactose, starch, talc, stearic acid; for capsules: tartaric acid or lactose;
for injectable solutions: water, alcohols, glycerin, vegetable oils; for suppositories: natural or hardened oils or waxes.
There is also provided a process for the preparation of such a pharmaceutical composition which comprises mixing the ingredients.
Utility
A further aspect of the invention is the use of a compound according to the invention, an enantiomer thereof or a pharmaceutically acceptable salt thereof, in the manufacture of a medicament for the treatment or prophylaxis of one of the below mentioned diseases or conditions; and a method of treatment or prophylaxis of one of the above mentioned diseases or conditions, which comprises administering a therapeutically effective amount of a compound according to the invention, or an enantiomer thereof or a pharmaceutically acceptable salt thereof, to a patient.
Compounds according to the invention are agonists of nicotinic acetylcholine receptors. While not being limited by theory, it is believed that agonists of the xcex17 nAChR (nicotinic acetylcholine receptor) subtype should be useful in the treatment or prophylaxis of psychotic disorders and intellectual impairment disorders, and have advantages over compounds which are or are also agonists of the xcex14 nAChR subtype. Therefore, compounds which are selective for the xcex17 nAChR subtype are preferred. The compounds of the invention are indicated as pharmaceuticals, in particular in the treatment or prophylaxis of psychotic disorders and intellectual impairment disorders. Examples of psychotic disorders include schizophrenia, mania and manic depression, and anxiety. Examples of intellectual impairment disorders include Alzheimer""s disease, learning deficit, cognition deficit, attention deficit, memory loss, and Attention Deficit Hyperactivity Disorder. The compounds of the invention may also be useful as analgesics in the treatment of pain (including chronic pain) and in the treatment or prophylaxis of Parkinson""s disease, Huntington""s disease, Tourette""s syndrome, and neurodegenerative disorders in which there is loss of cholinergic synapses. The compounds may further be indicated for the treatment or prophylaxis of jetlag, for use in inducing the cessation of smoking, and for the treatment or prophylaxis of nicotine addiction (including that resulting from exposure to products containing nicotine).
It is also believed that compounds according to the invention are useful in the treatment and prophylaxis of ulcerative colitis.
Pharmacology
The pharmacological activity of the compounds of the invention may be measured in the tests set out below:
Test Axe2x80x94Assay for Affinity at xcex17 nAChR Subtype
[125I]-xcex1-Bungarotoxin (BTX) Binding to Rat Hippocampal Membranes.
Rat hippocampi were homogenized in 20 volumes of cold homogenization buffer (HB: concentrations of constituents (mM): tris(hydroxymethyl)aminomethane 50; MgCl2 1; NaCl 120; KCl 5: pH 7.4). The homogenate was centrifuged for 5 minutes at 1000 g, the supernatant was saved and the pellet re-extracted. The pooled supernatants were centrifuged for 20 minutes at 12000 g, washed, and resuspended in HB. Membranes (30-80 xcexcg) were incubated with 5 nM [125I]xcex1-BTX, 1 mg/mL BSA (bovine serum albumin), test drug, and either 2 mM CaCl2 or 0.5 mM EGTA [ethylene glycol-bisxcex2-aminoethylether)] for 2 hours at 21xc2x0 C., and then filtered and washed 4 times over Whatman glass fibre filters (thickness C) using a Brandel cell harvester. Pretreating the filters for 3 hours with 1% (BSA/0.01% PEI (polyethyleneimine) in water was critical for low filter blanks (0.07% of total counts per minute). Nonspecific binding was described by 100 xcexcM (xe2x88x92)-nicotine, and specific binding was typically 75%.
Test Bxe2x80x94Assay for Affinity to the xcex14 nAChR Subtype
[3H]-(xe2x88x92)-Nicotine Binding. Using a procedure modified from Martino-Barrows and Kellar (Mol Pharm (1987) 31:169-174), rat brain (cortex and hippocampus) was homogenized as in the [125I]xcex1-BTX binding assay, centrifuged for 20 minutes at 12,000xc3x97g, washed twice, and then resuspended in HB containing 100 xcexcM diisopropyl fluorophosphate. After 20 minutes at 4xc2x0 C., membranes (approximately 0.5 mg) were incubated with 3 nM [3H]-(xe2x88x92)-nicotine, test drug, 1 xcexcM atropine, and either 2 mM CaCl2 or 0.5 mM EGTA for 1 hour at 4xc2x0 C., and then filtered over Whatman glass fibre filters (thickness C) (pretreated for 1 hour with 0.5% PEI) using a Brandel cell harvester. Nonspecific binding was described by 100 xcexcM carbachol, and specific binding was typically 84%.
Binding Data Analysis for Tests A and B
IC50 values and pseudo Hill coefficients (nH) were calculated using the non-linear curve fitting program AILFIT (DeLean A, Munson P J and Rodbard D (1977) Am. J. Physiol., 235:E97-E102). Saturation curves were fitted to a one site model, using the non-linear regression program ENZFITTER (Leatherbarrow, R. J. (1987)), yielding KD values of 1.67 and 1.70 nM for the 125I-xcex1-BTX and [3H]-(xe2x88x92)-nicotine ligands respectively. Ki values were estimated using the general Cheng-Prusoff equation:
Ki-[IC50]/((2+([ligand]/[KD])n)l/nxe2x88x921)
where a value of n=1 was used whenever nH less than 1.5 and a value of n=2 was used when nHxe2x89xa71.5. Samples were assayed in triplicate and were typically xc2x15%. Ki values were determined using 6 or more drug concentrations. The compounds of the invention are compounds with binding affinities (Ki) of less than 1000 nM in either Test A or Test B, indicating that they are expected to have useful therapeutic activity.
The compounds of the invention have the advantage that they may be less toxic, be more efficacious, be longer acting, have a broader range of activity, be more potent, produce fewer side effects, are more easily absorbed or have other useful pharmacological properties.